1. Field of the Invention
The invention relates to a method for adjusting wicket gates.
2. Description of the Related Art
Wicket gates, sometimes referred to as guide vanes, are used with turbines to control flow regulation over incoming or outgoing operating fluids. A typical turbine includes a wicket gate assembly arranged in a circle around the turbine axis. This assembly includes a plurality of wicket gates and how they are adjusted, one to another, and provides the desired flow regulation to the turbine. For example, in a water turbine all gates operate in unison and equally distribute incoming water, or outgoing water, when operating as a pump to, or from, a unit runner.
Typically, the orientation of each wicket gate is adjustable around a stem axis. Each wicket gate has a wicket gate operating lever. These wicket gate operating levers are connected to a common gate operating ring via connection links for synchronous rotation of all gates during opening or closing. Eccentric pins are provided at all operating ring connection points for individual wicket gate adjustments. Such a design is disclosed in U.S. Pat. No. 4,210,408 (Nace). Other conventional means of adjusting individual wicket gates includes using a turnbuckle.
Conventional methods of adjusting the individual wicket gates include the "banding" and "trial and error" methods.
The "banding" method requires removal of all operating levers, which frees the wicket gates. Cables are draped around the wicket gate circle exterior and pulled with chain hoists or other adequate means to force all the Wicket gates closed.
The "banding" method often does not prove successful. For example, the upper and lower gate side seals may resist movement and not allow proper intermeshing actions for closing. Moreover, a sledgehammer or other large object is often used to nudge the gates which can deform the bushings and surfaces of the gates. The cables used in banding may also deform the bushings and surfaces of the gates.
In a trial and error method, adjustment is difficult, because any change on one particular gate influences adjoining gates. Many times, a small relative clearance may exist which requires several gates in an area to be adjusted, and the final readings do not always reveal the anticipated results. Moreover, the trial and error method is time consuming and often several days are required to adjust the wicket gates.
The known "banding" and "trial and error" methods often do not result in a sufficient variance among the wicket gates.